First time hydro - is this high pH?

I've grown a few times in soil with good success, so I decided that I'd try a couple of hydro plants this time around to experiment in addition to the soil plants. All of these plants were started from seed at the same time.

The soil plants are doing fantastic, but the hydro plants are definitely not doing so great. They are significantly stunted compared to the soil plants and have some burning but I've been on the cautious side when using nutrients so I don't think it's over-nute. They are almost 4 weeks old and I've only given each plant around 4 tsp of Fox Farm Grow Big total so far. Each pot holds around 1 gallon of water total.

I think the problem is that I've been using water adjusted for the same pH as the soil plants (6.5-6.8 ) and after doing some more research, it looks like that hydro plants need more like 5.5-5.8 and that the hydroton I used has a tendency to raise pH. Does this look like high pH? If so, how do you recommend fixing it since there is no reservoir to take water out of?

all the 'research' you need is right there. They seem to like the ph ,burnt bits from over fert.

*BUDS said:

all the 'research' you need is right there. They seem to like the ph ,burnt bits from over fert.

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4 tsp of nutes over 4 weeks is too much? I was just following the directions on the Grow Big bottle and reducing it by about 1/3 because I know that over-nute is common for first timers.

You really need to use a TDS meter to know what PPM your nutes are at. they do look a bit burnt. If you have been keeping the PH at a constant 5.5-5.8 well PH isn't your problem. For my vegging plants i start feeding at 300-400PPM, by the time I switch to Flower Im at 1000PPM. in 4 weeks my plants are 3 feet tall, and yours should be at least double the size of your soil plants, you have some problems. What kind of lighting are you using? What kind of hydro setup? (looks like a mini flood and drain, but i can't be sure)

NoDrama said:

You really need to use a TDS meter to know what PPM your nutes are at. they do look a bit burnt. If you have been keeping the PH at a constant 5.5-5.8 well PH isn't your problem. For my vegging plants i start feeding at 300-400PPM, by the time I switch to Flower Im at 1000PPM. in 4 weeks my plants are 3 feet tall, and yours should be at least double the size of your soil plants, you have some problems. What kind of lighting are you using? What kind of hydro setup? (looks like a mini flood and drain, but i can't be sure)

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Good advice + Rep

NoDrama said:

You really need to use a TDS meter to know what PPM your nutes are at. they do look a bit burnt. If you have been keeping the PH at a constant 5.5-5.8 well PH isn't your problem. For my vegging plants i start feeding at 300-400PPM, by the time I switch to Flower Im at 1000PPM. in 4 weeks my plants are 3 feet tall, and yours should be at least double the size of your soil plants, you have some problems. What kind of lighting are you using? What kind of hydro setup? (looks like a mini flood and drain, but i can't be sure)

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I have a TDS meter that I've used but the problem is that the readings don't appear to be accurate. I say this because I have to stick the TDS meter in the hydroton directly. When I first set up the pots, I put filtered water around 70ppm that had a pH of around 6.8 but when I put the TDS meter directly into the pot with the hydroton and 70ppm water, it read like 700ppm BEFORE adding nutes. I thoroughly rinsed the hydroton before using it.

I just took a TDS reading of both pots and they're both over 1000ppm but I just don't think that's accurate because of that first reading I did before adding nutes. Is there a more accurate way of reading the PPM using hydroton as medium?

jugg1es said:

I have a TDS meter that I've used but the problem is that the readings don't appear to be accurate. I say this because I have to stick the TDS meter in the hydroton directly. When I first set up the pots, I put filtered water around 70ppm that had a pH of around 6.8 but when I put the TDS meter directly into the pot with the hydroton and 70ppm water, it read like 700ppm BEFORE adding nutes. I thoroughly rinsed the hydroton before using it.

I just took a TDS reading of both pots and they're both over 1000ppm but I just don't think that's accurate because of that first reading I did before adding nutes. Is there a more accurate way of reading the PPM using hydroton as medium?

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You definitely need to always have the proper PH and TDS calibration solutions. You won't know if its correct or not until you calibrate it with the special solution. Walk, no run, to the nearest hydro shop and get calibration solutions. Calibrate every month at least. Your TDS meter could very well be reading correctly, I only add about 2 tablespoons of nutes for each of my 25 gallon Reservoirs and it gives me a PPM reading of 800 and a EC rating of 1.09. I like EC better than PPM, so try to get your EC under .7 for new vegging plants, increase by .2 each week when you change out reservoirs.

NoDrama said:

You definitely need to always have the proper PH and TDS calibration solutions. You won't know if its correct or not until you calibrate it with the special solution. Walk, no run, to the nearest hydro shop and get calibration solutions. Calibrate every month at least. Your TDS meter could very well be reading correctly, I only add about 2 tablespoons of nutes for each of my 25 gallon Reservoirs and it gives me a PPM reading of 800 and a EC rating of 1.09. I like EC better than PPM, so try to get your EC under .7 for new vegging plants, increase by .2 each week when you change out reservoirs.

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I've already calibrated it. And the TDS meter that I have is actually an EC meter, but it has a feature to calculate PPM based on temperature from the EC values it gets.

I think the TDS meter is fine, but how do you explain the almost 10x jump in PPM when 70 ppm water was added to hydroton WITHOUT adding any nutrients? I don't understand why *supposedly* inert hydroton caused the PPM to jump so high without adding any nutrients. I literally tested the water at 70ppm, then poured it into the hydroton and then stuck the TDS meter in teh hydroton/water mixture and it read 700ppm without adding anything else.

My original question was whether or not the plants looked like they were having pH problems but it seems like a consensus that it looks more like over-nutes. How high does the pH have to be for plants to show problems?

In hydro if your hitting over 6.2 you'll probably start to see problems, but if it gets really low then you will see problems really fast. Trust the meter, its the only thing you got and if you calibrated it then I would have no worries. Your changing out your nutes in the res every week right?

NoDrama said:

In hydro if your hitting over 6.2 you'll probably start to see problems, but if it gets really low then you will see problems really fast. Trust the meter, its the only thing you got and if you calibrated it then I would have no worries. Your changing out your nutes in the res every week right?

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well, this hydro method is just a straight up hydroton planter so there is no reservoir. It's just a pot with hydroton and water in it and I never built in a way to drain the water from it easily. I didn't have space for a reservoir in the grow box so I found a method that didn't require it, but it was for food crops and wasn't intended for marijuana. Now that I think about it, it doesn't really seem like a good method for cannabis, it was just convenient. I'm going to rethink my design and see if I can change to a resevoir method without killing the plants. thanks man, you've been a ton of help. +rep

Oh yeah your probably having problems with stagnant water then, probably have some root rot, that would explain the stunted growth. Get a res, always change out all the water weekly, and for god sakes make sure you have an airstone pumping bubbles in that res and under your plant roots. Amazing growth guaranteed if you do those things.

Check ebay for ph/tds meters. I bought the Hanna Gro Check combo meter for $60! They cost like $150-180 new at the store. Ive had it for over a month now and havent had any problems with it. The guy I bought it from had a bunch too I think

NoDrama said:

Oh yeah your probably having problems with stagnant water then, probably have some root rot, that would explain the stunted growth. Get a res, always change out all the water weekly, and for god sakes make sure you have an airstone pumping bubbles in that res and under your plant roots. Amazing growth guaranteed if you do those things.

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So I built a reservoir and tried to hook my plants into it. I had to drill holes and seal them with a plant already in the pot, which is tough, and I ended up losing one of the plants (the smallest one thankfully). the other one hasn't died yet but I haven't seen a large improvement yet, only time will tell.